Of the two major classes of metabolic fuels, glucose and lipids, more research has been done on the role of glucose in the control of eating behavior. There is substantial evidence that dietary and endogenous fats modify eating in rats. However, while it is known that alterations in the intracellular utilization of glucose provide a signal controlling food intake, much less is known about the mechanism of action of lipids. Numerous observations suggest that oxidation of fat fuels provide a signal controlling food intake. We plan to examine this relationship further by studying the effects on food intake of dietary fats, administration of pure fat and fats mobilized from internal reserves in normal and diabetic rats. Measurements of plasma metabolic fuels will help to characterize metabolic effects and will provide indices of fat oxidation. The role of fat fuel oxidation in the control of eating will be tested by assessing quantitative relationships between metabolic changes and food intake. By varying the type of fat used, by manipulating metabolism with insulin treatment and by pharmacologic inhibition of fatty acid oxidation. These studies should provide basic information on metabolic factors involved in the control of food and caloric intake.